FIGS. 3 and 4 show a structure in which a roof 1, a retractable roof of a stadium or arena comprises a plurality of roof sections 1a through 1d which are laid or telescoped over each other when they are retracted and which form a single unitary roof structure when expanded. Sliding roof sections 1a through 1c are supported at both ends on rails Ra through Rc formed on steps in the upper portion of the building. Sliding roof sections 1a through 1c are retracted by automating a movable support 50 or winching them with cables. It is evident that the roof is exposed to external stress from thermal expansion or thermal shrinkage due to the environmental temperature changes, causing displacement in the joint between rails Ra through Rc and movable support 50. As a result, the roof is exposed to external stresses from twisting, lifting, or tension forces, making a smooth drive movement of the roof sections difficult.
To lessen the influence from such various external stresses, the roof of conventional technology has a structure such as that shown in FIG. 5. In a front elevational view, support frame 56 is mounted with base 52, which supports sliding roof section 1a via a universal joint 55 connected by means of pins 53 and 54 arranged substantially parallel to a rail Ra and substantially perpendicular to the rail Ra. Support frame 56 also includes a drive wheel and follower wheel 57, which move along rail Ra. The support frame 56 also includes guide wheels 58, which move along side guide rails Rg.
In the movable support of FIG. 5, as is the case for a bogie car, the tolerance for absorbing the distortion due to the external stress is created by arranging pins 53 and 54 substantially parallel to rail Ra and substantially perpendicular to the rail Ra. Nevertheless, this level of tolerance is not sufficient to reduce the influence of external forces coming from different directions. This requires a larger tolerance for absorbing stress.
The apparatus incorporating the principles of the present invention resolves the problem and provides a movable support for the retractable roof which can transmit the movement of the movable support to the sliding roof sections with little tolerance. It also provides a movable support which is capable of reducing the influence from external forces coming from different directions and can tolerate a relatively larger distortion and displacement.